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I recently purchased a 2007 FJ cruiser up here in the north where we use lots of salt. The only issue I noticed with this vehicle (and about half of the FJs I looked at) was rust developing along the welds in the frame.

What would be a good approach to getting control of this problem? Make that a practical approach, I am not going to take the body off the frame and have it sand blasted and powder coated.

Would it be reasonable to have it undercoated or treated in some way?

I know that some undercoating is actually worse because it traps moisture and salt against the metal, is there a good option?

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You can use some POR15 which will stop the rust from spreading. It is really good on surface rust. I'm currently using it on my 1987 Toyota Land Cruiser and works well!

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Remember to follow the prep instructions - – Mark Johnson Apr 12 '12 at 5:32

You would be wise to get your vehicle on a hoist and clean up the rusted areas with a wire brush/grinder of various sizes. You can then apply primer or go straight to rubberized undercoat.

From there you would be ok to to get your vehicle undercoated from a shop. The key to this is cleanliness. Make sure your vehicles undercarriage is properly rinsed before the undercoat is sprayed.

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